This invention relates to the capture of energy from waves on the surface of a body of water and, particularly, to a power generating system using a sub-surface energy capturing element.
Various systems are now known for capturing energy from waves passing along the surface of a body of water, particularly an ocean where quite large and powerful waves are consistently present. Typically, such systems comprise a float or buoy which floats directly on the water surface and which rises and falls with the passing waves. The float thus experiences an upward force with a rising wave, and the weight of the float can exert a downward force with a falling wave. The float associated forces are used in various arrangements for mechanically driving a transducer for converting the mechanical forces and associated mechanical energy to useful forms of energy, e.g., electrical power.
While the floats typically remain on the water surface, for maximum energy capture from the passing waves, it is known (as discussed in U.S. Pat. No. 5,578,889 to Epstein) to deliberately completely submerge the float during storm conditions for protecting the float from damage by extremely rough and violent surface conditions. In recognition of the fact that water pressure variations, and attendant circulatory water flows, are present within the water at depths lower than the wave troughs, the patent discloses submerging the float deep enough for protection against wave violence, but not so deep as to be outside the wave energy zone. Thus, energy is generated, but at reduced levels, even when the float is removed from its normal position on the water surface. Submerging the float from its normal surface position thus requires, in the patent arrangement, means for changing the normal buoyancy of the float from its usual non-storm operating conditions. The provision of such buoyancy changing means tends to be rather complex and, for practical reasons, can be used only with quite large and expensive power generating systems.
In smaller systems, particularly for the generation of relatively small amounts of power, e.g., for trickle charging a storage battery, provision of such buoyancy changing means is quite impractical.